Auto merge of #44585 - frewsxcv:rollup, r=frewsxcv

Rollup of 23 pull requests

- Successful merges: #44131, #44254, #44368, #44374, #44378, #44388, #44430, #44450, #44453, #44472, #44476, #44477, #44485, #44497, #44521, #44534, #44536, #44541, #44552, #44559, #44563, #44569, #44572
- Failed merges:

1 files changed, 23 insertions, 1 deletions

diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 1708f3e3987..46b96df1eab 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -622,6 +622,13 @@ impl String {
     /// Decode a UTF-16 encoded slice `v` into a `String`, replacing
     /// invalid data with the replacement character (U+FFFD).
     ///
+    /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
+    /// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8
+    /// conversion requires a memory allocation.
+    ///
+    /// [`from_utf8_lossy`]: #method.from_utf8_lossy
+    /// [`Cow<'a, str>`]: ../borrow/enum.Cow.html
+    ///
     /// # Examples
     ///
     /// Basic usage:
@@ -759,7 +766,22 @@ impl String {
         self
     }
 
-    /// Extracts a string slice containing the entire string.
+    /// Converts a `String` into a mutable string slice.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// use std::ascii::AsciiExt;
+    ///
+    /// let mut s = String::from("foobar");
+    /// let s_mut_str = s.as_mut_str();
+    ///
+    /// s_mut_str.make_ascii_uppercase();
+    ///
+    /// assert_eq!("FOOBAR", s_mut_str);
+    /// ```
     #[inline]
     #[stable(feature = "string_as_str", since = "1.7.0")]
     pub fn as_mut_str(&mut self) -> &mut str {